The present invention relates to a rear projection screen suitable for use as, for example, a screen for video projectors and, more particularly, to a rear projection screen having a greater angular field of vision on the viewing side and an increased brightness. Still more particularly, the invention is concerned with a lenticular lens for use in a rear projection screen of the type mentioned above.
Rear projection screens have been widely available for video projectors, microfilm readers and computer display systems, and various studies and attempts have been made for improving the light transmitting characteristics of the rear projection screen for attaining a greater angular field of vision, higher contrast and higher resolution. As a measure for achieving these objects, it has been proposed to use, solely or in combination with a lens or a diffusion plate, a lenticulated surface having a multiplicity of minute cylindrical lenses (lenticules) arranged continually.
This lenticulated surface is effective in diffusing the light impinging thereon. More specifically, a lenticulated surface having a multiplicity of minute vertically extending cylindrical lenses arranged continually on a vertical plane laterally diffuses the light, while the lenticulated surface having a multiplicity of minute horizontally extending cylindrical lenses arranged continually on a vertical plane longitudinally diffuses the light. When this lenticulated surface is used as a screen, the maximum diffusion angle is varied largely depending on whether the lenticulated surface is faced to the incident light, i.e. towards the light source or to the viewer. Namely, as is known to those skilled in the art, it is possible to obtain a greater diffusion angle when the surface is faced to the light source than when the same is faced to the viewer.
In general, however, each lenticule of the lenticulated surface of the kind described has a circular cross-section so that the angle of diffusion of light is considerably small. In consequence, the brightness is drastically lowered disadvantageously in the region of viewing angles exceeding 30.degree., as will be seen from FIG. 14. This reduction of brightness causes not only the problem that the picture surface is darkened when viewed from the region out of the viewing angle of 30.degree. but also a problem that the picture surface becomes completely invisible due to a surface reflection in bright circumstance under the influence of ambient light.